Skimmilk crossflow microfiltration performance versus permeation flux to wall shear stress ratio

Principles of Membrane Filtration

“…An approximation that allows for experimental determination was defined by Le Berre & Daufin (1996):…”

“…Here, the ratio J/τ w defines the balance of particle deposition rate (relating to J ) and particle removal rate (relating to τ w ) and, therefore, determines particle transport towards the deposit layer (Altmann & Ripperger, 1997). If a critical value of J/τ w is exceeded, membrane processes become unsteady, thus operating conditions are recommended in which J/τ w is below that critical value (Le Berre & Daufin, 1996;Grandison et al ., 2000). This value varies with pore size, membrane material and feed composition, and needs to be determined experimentally for every membrane feed combination (Grandison et al ., 2000).…”

“…Both, the lift force and the filtrate drag force increase with particle size; however, lift force increases with the third power of the particle size and drag force with the first (Altmann & Ripperger, 1997). Consequently, at high values of wall shear stress, larger particles are preferentially removed from the surface compared with smaller ones and the filter cake becomes enriched with small particles, leading to a lower porosity of the cake layer and decreasing effective pore size (Le Berre & Daufin, 1996;Ripperger & Altmann, 2002). Flux of polydisperse suspensions is often similar to that of a monodisperse suspension of the smallest particle (Kromkamp et al ., 2002).…”

“…An example of its effect on retention is the MF of skim milk to separate caseins from whey protein. It was found that at a low value for J/τ w (<0.8 L h −1 m −1 Pa −1 ), casein retention is low and at high values (>1.0 L h −1 m −1 Pa −1 ) whey protein permeation is reduced (Le Berre & Daufin, 1996). Therefore, an ideal value of J/τ w for the size separation of two species exists.…”

Einfluss des Membranwiderstands auf die Filtrationsleistung bei der Proteinfraktionierung entlang von Mikrofiltrationsmodulen

“…Obwohl es beim Einsatz der Querstromtechnik zu einem kontinuierlichen Abtrag von deckschichtbildendem Material kommt, ist es bisher noch nicht gelungen, Deckschichtbildung bei der Filtration wässriger Biopolymersysteme vollständig zu vermeiden. Die bisherigen Ansätze, den Deckschichtbildungsprozess zu erklären, gehen meist von homogenen Filtrationsbedingungen entlang der Membran und daher auch von einem einheitlichen Deckschichtaufbau aus [1,2]. Bei der Querstromfiltration kommt es jedoch zu einem retentatseitigen Druckabfall und dadurch auch zu einer abnehmenden transmembranen Druckdifferenz Dp TM entlang der Membran [3].…”